The gift from the Lucasfilm Foundation is the largest in the school's history, USC officials announced Tuesday. His donation topped the previous school record of $120 million, made in 1993 by Walter Annenberg.
Lucas, 62, graduated from USC in 1966.
The foundation is giving $75 million for the construction of a 137,000-square-foot, state-of-the-art home for the university's acclaimed cinema school. The remaining $100 million is to be used to endow the school.
"I discovered my passion for film and making movies when I was a student at USC in the 1960s, and my experiences there shaped the rest of my career," Lucas said in a statement.
"I'm also an ardent advocate for education at all levels and encouraging young people to pursue their ambitions by learning. I'm very fortunate to be in a position to combine my two passions and to be able to help USC continue molding the futures of the moviemakers of tomorrow."
A groundbreaking ceremony for the school's new building is scheduled for Oct. 4.
Lucas' gift was announced just hours after the Tournament of Roses in Pasadena said he would be the grand marshal of next year's Rose Parade.